Answer: Big leaf hydrangeas produce flowers on new shoots which develop on old wood. If your hydrangeas die down to the ground during the winter months, or if you prune them all the way down, there will be no old wood from which new flowering shoots can develop. They may never bloom for you! Or, in the case of the smaller shrubs, the blooms will be coming from growth on the old wood which is lower down on the shrub.
Endless Summer hydrangeas bloom on either new or old wood so even if they die down to ground level every year you will still get loads of blooms. Maybe it's time to replace your non-blooming hydrangeas?
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